Why are neurons an “animals only” phenomenon? Big Questions Characteristics of a nervous system

fastaccuratereset quickly Structure fits functionmany entry points for signalone path outtransmits signal Most specialized cell in animalsLongest cellblue whale neuron: 10-30 metersgiraffe neuron: 5 metershuman neuron: 1-2 meters Fun facts about neurons Think dominoes!1. start the signal-knock down line of dominoes by tipping 1st one2. propagate the signal-do dominoes move down the line? no, just a wave through them!3. re-set the system-before you can do it again, have to set up dominoes again The Neuron has a similar systemprotein channels are set up1. once the first one is opened, the rest open in succession2. a “wave” action travels along neuron3. have to re-set channels so neuron can react again Cells live in a sea of charged ions

more concentrated within the cellanions (negative)K+charged amino acids (aa-)

more concentrated in the extracellular fluidcations (positive)Na+Cl- Opposite charges on opposite sides of cell membrane

Serotoninwidespread in brainaffects sleep, mood, attention & learning Compare the regulatory structures and functions of the nervous and endocrine systems

Diagram the processes by which nervous signals are transmitted by and between neurons.

Label all parts of a neuron

Explain the causes and effects of major disruptions to neuron function Make Sure You Can The need for fast,long-distance messages Dendrites Neurons Do These Things! sensory neuron Interneuron Motor Neuron Signal moves from black to red Glial cells help neurons neurons stained with "Brainbow" flourescence Incoming signals enter here.Each dendrite is connected to another neuron at a synapse Cell Body Axon Hillock Myelin Sheath Schwann Cell Node of Ranvier Nerve Terminals Axon How membrane potential is measured Lots of pump proteins and ion channels Maintain concentrations of ions

Reset concentrations following nerve signal

Different kinds of "gates" control the openings to the channels:mechanical gates: Opened by forcevoltage gates: Opened by voltageligand gates: Opened by ligand binding Summary Action Potential A nerve signalElectrical (ion exchange)Binary (all or nothing) Action Potential Propagation Incoming Impulses Come in 2 Flavors Excitatory or Inhibitory An "All or None" Signal Neural membrane polarity is constantly fluctuating around the resting potential.

For an action potential to be generated, the membrane must be depolarized to a "threshold potential". Action Potential Generation 1. Neuron is at rest:All gated channels are closed

2. Neuron Depolarizes:Na+ gated channels begin to open.

3. Rising Phase of AP:Na+ gated channels all open.

4. Falling Phase of AP:Na+ gates shut. K+ gates open

5. Undershoot:K+ gates begin to close. Na/Kpump restores resting potential "Na+ in, K+ out" Action potential travel by jumping ("saltations") between Schwann cells. Multiple Sclerosis:Results from De-mylenation of motor neurons Layers of Myelin insulate neurons.Speeds Transmission of AP's Saltatory Conduction Major Neurotransmitters Snake venom (green) blocking the active site of acetylcholinesterase Cone Snail Venom Blocks Na+ channels on post synaptic neurons Why are axons so long?Why have synapses at all?How do “mind altering drugs” work?caffeine, alcohol, nicotine, marijuana…Do plants have a nervous system?Do they need one? Any Questions?Yes! Complexity Emerges! So Cool! Contains all organelles for the neuron. Signals move from Dendrites to cell body to axon to nerve terminals Where an Action Potential begins (if it's going to). The Action Potential moves through the Nodes of Ranvier by saltatory conduction The start of the axon. Modes of action of some of the major venoms